The present invention is related to electrical connectors and more particularly to connectors for coaxial cable having a corrugated outer conductor.
Generally coaxial cable includes an inner conductor surrounded by a layer of dielectric material and precisely centered within an outer conductor, and having an outer jacket of dielectric material. In certain coaxial cable, the outer conductor defines a ground return path necessary for microwave signal transmission, and is termed semirigid coaxial cable. In certain semirigid coaxial cable, the outer conductor is strengthened by corrugation, and in certain such cable the corrugation is helical, as is described in proposed draft Military Specification MIL-C-28830/AA. U.S. Pat. No. 5,154,636 discloses a connector for such cable includes a forward connector assembly with an inner contact disposed within a dielectric insert in an outer conductive housing, with the outer housing including a rearwardly extending threaded flange in which a flaring ring is disposed. A rear connector portion is assembled separately to the cable end, and comprises a clamping member having a threaded inner surface to match the helical corrugations of the outer cable conductor. The flaring ring has an inner diameter at least as small as the inside diameter of the helically corrugated outer cable conductor, and includes a bevelled end which engages the inner surface of the open end of the outer cable conductor to flare the engaged portion outwardly against a complementarily bevelled surface along the forward end of the clamping member, as the forward connector assembly is threaded onto the end of the clamping member. U.S. Pat. No. 5,137,470 discloses a similar connector.
Other connectors for coaxial cable with helically corrugated outer conductor are disclosed in U.S. Pat. Nos. 3,199,061; 4,047,291; 4,995,832 and 4,824,400. Additional connectors for coaxial cable having an annularly corrugated outer conductor are disclosed in U.S. Pat. Nos. 4,046,451 and 4,800,351.
It is desired to provide a coaxial connector for coaxial cable having a corrugated outer conductor which is easily assembled thereto and mechanically secured thereto.
It is further desired to provide such a connector which is easily assembled to the cable without deforming the outer conductor of the cable and which assures an electrical connection of the inner surface of the outer conductor with the outer conductive housing of the connector.
The present invention includes a connector having a forward or mating portion of standard or conventional configuration, and a rearward portion adapted to receive a prepared cable end thereinto. The rearward portion includes a bushing entrapped within a sleeve of the outer conductive housing of the connector and cooperatively receives the corrugated cable outer conductor thereinto for being either crimped thereagainst or soldered thereto to establish an assured ground connection therewith as well as a mechanical connection thereto. The bushing is initially C-shaped in cross-section which is manufactured to be disposed in the sleeve of selected inner diameter so that the axial slot is partially open to initially define a gap of selected spacing, with the bushing fabricated such that the general inner diameter after assembly within the sleeve is related closely to the general outer diameter of the cable outer conductor.
The interior surface is profiled into alternating ridges and grooves to match the corrugations of the outer conductor of the coaxial cable, and initially permits the cable end to easily be inserted thereinto until the inner conductor is matingly received into a socket contact section of the forward connector portion and the end of the cable""s outer conductor abuts an annular interior flange of the sleeve. In a first embodiment, the sleeve is then crimped with crimp tooling against the bushing, urging the bushing against the corrugated cable outer conductor at least substantially closing the axial slot and compressing the ridges of both the cable conductor and the bushing into the opposing grooves of the other in an interference fit. The gap of the axial slot is precisely dimensioned to permit sufficient reduction in bushing inner diameter so that the general inner diameter of the bushing complements the outer diameter of the cable outer conductor to define a compression fit with controlled slight deformation of the outer conductor, with either the crimp tooling or ultimately the closing of the axial slot acting to control crimping to avoid deformation of the cable outer conductor into the underlying insulation. In another embodiment, the sleeve and bushing include one or more aligned apertures radially thereinto through which solder or conductive epoxy may be deposited to flow between the bushing inner surface and the cable outer conductor outer surface and harden or cure.
In a particular embodiment of the present invention for use with cable having a helically corrugated outer conductor, the interior surface of the bushing is threaded to have a pitch equivalent to the pitch of the helically corrugated outer conductor, and has a general inner diameter permitting the cable end to be threaded into the bushing without undue effort. The cable end is threaded into the bushing held within the sleeve until the inner conductor is matingly received into a socket contact section of the forward connector portion and the forward edge of the outer conductor abuts a rearwardly facing surface of an annular interior flange of the sleeve. This embodiment is useful with either the crimping or soldering approaches.
Where the connector is to be crimped onto the cable, the bushing""s interior surface is profiled to define a helical ridge or thread and associated helical groove, with the profile precisely dimensioned to assure that upon crimping the surfaces defining the groove of the bushing abut and are compressed into the opposing surfaces of the ridge of the cable outer conductor, but the surfaces defining the ridge of the bushing does not engage the surfaces defining the groove of the cable outer conductor. Such arrangement assures that the bottom of the groove of the cable outer conductor is not engaged and deformed radially inwardly and into the insulative foam, while controllably deforming the ridge of the cable outer conductor to a limited extent to clinch the crest of the ridge which does not deform into the insulative foam and does not affect impedance of the cable. The leading edge of the outer conductor, which is initially urged tightly against the annular flange of the sleeve containing the bushing when threaded into the adapter, is pressed even more tightly thereagainst further enhancing the electrical connection of the inner surface of the outer conductor at a plurality of points about the circumference between the inner surface of the cable outer conductor and the connector outer conductive housing.
In one particularly useful form of the present invention, the forward connector portion is a subassembly including the inner contact within a dielectric housing, and the rear face of the portion includes a threaded annular flange. The rearward connector portion includes a forwardly extending annular flange complementarily threaded to be threaded onto the annular flange of the forward connector portion. Thus the rearward subassembly can be dimensioned to the specific size of the cable, while the forward subassembly can be one selected from several varieties thereof having standardized threaded flanges, in modular fashion. The modular arrangement permits utilization of the same rearward subassembly with a right angle forward connector configuration, for example, or one having a socket style or a pin style forward inner contact section as desired, or one having a circuit board mountable forward contact section.
It is an objective of the present invention to provide a coaxial connector suitable for use with semirigid coaxial cable of the type having corrugated outer conductor.
It is also an objective to provide such a connector for use with cable having a helically corrugated outer conductor.
It is additionally an objective to provide a coaxial connector crimpable to a corrugated cable outer conductor with only slight deformation of the cable outer conductor radially inwardly toward the inner conductor and yet establishing an assured mechanical and electrical connection.
It is also an objective to provide a coaxial connector which is solderable to a corrugated cable outer conductor to establish an assured mechanical and electrical connection.
It is a further objective to provide a cable-engaging connector portion which can be utilized in modular fashion with one of a variety of forward connector portions.
Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings.